Air intake silencer



Feb. 11, 1964 E. F. LIRETTE Y AIR INTAKE SILENCER Filed May 3, 1961INVENTOR.

EDWARD F. LIRE TE BY M ATTORNEY United States Patent M 3,120,876 AIRINTAKE SILENCER Edward F. Lirette, Ann Arbor, Mich, assignor to theUnited States of America as represented by the Secretary of the AirForce Filed May 3, 1961, Ser. No. 107,602 3 Claims. (Cl. 181-50) Thisinvention relates to the attenuation of noise by the containment andharmless dissipation into heat of the acoustic energy generated by anoffending machine. While this invention is specifically in connectionwith a neumatic blower supplying cooling air for use on airground-support equipment, it is equally applicable to other equipmentwith comparable noise generating propensities. This invention isapplicable to air and other gaseous fluid handling machines, the termgas being construed to include all non-solid and non-liquid mediums.

Noise emissions from machines may be merely annoying or they may behazardous. Annoying or nuisance noise will produce no serious auditoryeffect although there may be physiological effect. However, this is nottrue of hazardous noise which will produce serious auditory effectsincluding auditory or non-auditory physio logical reactions depending onthe character of the noise.

Among the consequences of hazardous noises are temporary or permanentloss of hearing and the masking of one sound by another.

The ability of the ear to hear two sounds at one time is a physiologicalphenomenon. However, this function, which provides for thediscrimination between sounds, is subject to the effect of imposing onesound on another. This causes one of the sounds to become indistinct,or, as it may be said, auditory masking has occurred.

Connection with aircraft ground-support equipment, the masked soundswill be limited to speech and the masking sounds will therefore refer toany other sounds which may interfere with the speech signals from acommunications standpoint. It is apparent that any masking which wouldimpair a communication channel in such manner as to adversely affect thereceptability of orders, instructions and other vital information canlead to dire results.

Random noise such as generated by operating machinery is a moreeffective masker of speech than are pure tones at the samesound-pressure level. It is also known that low frequency noises have agreater masking effect than noises of high frequency.

The silencer embodied by this invention is of the absorptive type whichis broadly tuned and maintains its effectiveness over a wide range offrequencies and operating speeds.

The object of this invention is to attenuate the noise emitting frompneumatic machinery such as blowers and the like by providing a suitableinlet silencer.

Other objects will become more apparent from the following descriptionof the invention as depicted by the drawings in which:

FIG. 1 is an end view of the silencer; and

FIG. 2 is a vertical sectional View on line 2-2 of FIG. 1.

Referring to the drawings which illustrate a preferred embodiment of theinvention comprising a silencer removably secured to the inlet of ablower or like machine 8. The outer casing or shell 12 comprises atubular casing member 14 to one end of which is welded or otherwisejoined to an inlet ring 16. A truncated cone member 18 has its largerdiameter end welded or otherwise joined to the other end of easingmember 14. The smaller diameter of truncated cone member has welded orotherwise joined thereto a neck 20 to which is welded or otherwisejoined to a mounting flange 22. Mounting 3,120,870 Patented Feb. 11,1964 flange 22 must be formed to fit the particular application of thesilencer and the particular configuration used and does not constitutepart of this invention.

Inner cone 24 is formed to substantially the same slope as the truncatedcone 18 and is coaxially supported within the outer casing or shell 12by means of studs 26 which may be welded or riveted in place and withits apex directed downstream in the air flow. The inner cone is mountedin such longitudinal relationship with the outer casing or shell 12 aswill produce the least impedence to flow through the silencer.

The outer or splitter cone 28 is substantially smaller than inner cone24 and is spot welded or otherwise joined to inner cone 24 as shown withits apex directed upstream into the air flow. The slope of outer cone 28is such as will deflect impinging air and direct it toward thepassageway between inlet ring 16 and inner cone 24.

The interior surface of the outer casing or shell 12 is lined with soundabsorbing material 30 such as for example, Owens-Corning FiberglassPF-335, which may be held in place with hardware cloth or other meansknown to the art. Like sound absorbing material 32 is joined to thedownstream side of inner cone 24.

The particular sound-absorbing material used or method of attachmentform no part of this invention. Any suitable material may be used.

In operation, inflowing air will flow freely through the silencer whichwill at the same time attenuate and dissipate as heat, certain acousticenergy generated by the machine to which attached.

While the embodiment of this invention disclosed by the specificationand drawings has taken a given form, it is obvious that modificationsmay be made as dictated by the requirements of the specific machine onwhich the invention is to be used.

I claim:

1. A gas inlet silencer comprising an outer shell member, an inner conemember coaxially mounted within said outer shell member and with apexdirected downstream, gas passageway between the base periphery of saidinner cone member and said outer shell member, an outer cone member withbase periphery smaller than base periphery of said inner cone member,said outer cone member being coaxially mounted within said outer shellmember and with apex directed upstream, all inside surfaces of saidouter shell member and downstream surface of said inner cone memberbeing lined with a layer of sound absorbing material.

2. A gas inlet silencer comprising an outer shell member, an inner conemember coaxially mounted within said outer shell member, a plurality ofstruts joining said inner cone member and said outer shell member, saidinner cone member being mounted with apex directed downstream, gaspassageway between the base periphery of said inner cone member and saidouter shell member, an outer cone member with base periphery smallerthan base periphery of said inner cone member, said outer cone memberbeing coaxially mounted within said outer shell member with apexdirected upstream, all inside surfaces of said outer shell member anddownstream surface of said inner cone member being lined with a layer ofsound absorbing material.

3. In pneumatic machinery and the like, an inlet silencer comprising atubular casing member, an inlet ring joined to one end of said tubularcasing member, a truncated cone member joined to the other end of saidcasing member, a neck member joined to small periphery of said truncatedcone, means joined to said neck member for attaching to said machinery,an inner cone member coaxially mounted within said tubular casingmemher, a plurality of struts joining said truncated cone member andsaid inner cone member With apex directed downstream and providing anannular passageway between base periphery of said inner cone member andtubular casing member, means for directing inflowing air into said outercasing member, said means being a splitter cone coaxially mounted tosaid inner cone with its apex directed upstream, said splitter conehaving a base periphery smaller than the base periphery of said innercone, the inside surfaces of said tubular casing member, said inletring, said truncated cone, said neck and the downstream side of saidinner cone being lined with a layer of sound absorbing material.

UNITED STATES PATENTS Ricardo et a1. Nov. 13, 1917 Hamilton et a1. Oct.7, 1930 Hamilton et al. June 14, 1931 Day Apr. 21, 1936 Lysholm et al.Oct. 18, 1955 Meyer June 28, 1960 Audette July 4, 1 961 FOREIGN PATENTSGreat Britain Apr. 8, 1959 France Feb. 29, 1960

1. A GAS INLET SILENCER COMPRISING AN OUTER SHELL MEMBER, AN INNER CONEMEMBER COAXIALLY MOUNTED WITHIN SAID OUTER SHELL MEMBER AND WITH APEXDIRECTED DOWNSTREAM, GAS PASSAGEWAY BETWEEN THE BASE PERIPHERY OF SAIDINNER CONE MEMBER AND SAID OUTER SHELL MEMBER, AN OUTER CONE MEMBER WITHBASE PERIPHERY SMALLER THAN BASE PERIPHERY OF SAID INNER CONE MEMBER,SAID OUTER CONE MEMBER BEING COAXIALLY MOUNTED WITHIN SAID OUTER SHELLMEMBER AND WITH APEX DIRECTED UPSTREAM, ALL INSIDE SURFACES OF SAIDOUTER SHELL MEMBER AND DOWNSTREAM SURFACE OF SAID INNER CONE MEMBERBEING LINED WITH A LAYER OF SOUND ABSORBING MATERIAL.